Kerry Katona is a curious phenomenon. She is very famous indeed, in the sense that she appears in certain sectors of the press almost daily, but is also wholly mystifying in her appeal. She is ubiquitous, though it's not clear why. Just as opaque is why Channel 4 has decided to dedicate an hour's broadcasting schedule to her. The narrator offers a semi-justification that the point is to "see what it's like to be a celebrity once no one wants you", though really it's hard to spot any purpose beyond conventional slebrity voyeurism.

Presumably, the idea was dreamed up before Katona's makeover at the hands of the powers-that-be-behind-Hello!-cover-shoots. These days, Katona is positively wholesome – or so it seems from a quick skim of the latest red-top accounts. Last night, she was framed as something else altogether. The first we saw of her was a slouching shot in the kitchen, lighting a cigarette straight from the cooker. She did this film for free, we were told. Again, it's difficult to fathom why. Presumably her famous-for-nothing star had waned to the point whereby people would no longer pay to watch her behind closed doors. "At the end of the day, I've got to earn," she reflected. "I ain't got a clue what I do. Cheer people up because they read bad stuff about my life?"

It was a fairly astute analysis. Katona, it seems, is many things – but not stupid. Later on in the film, when her marriage to the tabloid-baiting former taxi driver Mark Croft unravelled, she was careful not to lay the blame on him. Well, not until a newspaper had paid a considerable sum for the gory details. Watching her strike the deal late at night, not having told her children and while still living with Croft, it was impossible not to be struck by the state of tension that must, permanently, dominate her life.

It's a very odd – and one suspects unsustainable – way to exist. If she does, as she claims, have manic depression the whole spectacle seems almost medieval in its lack of propriety. Should anyone be turned into a national freak show? Anyway, Kerry and Me was nothing new, really, certainly no more sensational than last year's notorious This Morning interview.

When we left Gareth Malone last week, our bespectacled hero had just about managed to convince his group of too-cool-for-school teens that joining the cast of an opera – an opera whose making was to be broadcast to the nation – was not, necessarily, an instant shortcut to social suicide. With the final 50 cast members chosen, and the writing of the brand-new script completed, everything seemed to have fallen into place with remarkable ease. Inevitably, it couldn't last. Could it?

In a word: no. Still, it took a while for the cracks to show. A visit to the Royal Opera House went reasonably well ("The food's good!" noted one of Gareth's more observant protégés). A series of one-on-one sessions with the teenagers to boost confidence meant that they were, at least, starting to get into the swing of things, despite the increasing pressure from production director John to live up to his high expectations. And even Stefan, the tuneless cast "reserve", is showing signs of improvement thanks, in large part, to his serious hard grafting. "It's like a massive Jackson Pollock," gushed Gareth, winningly. "All... splodgy."

Things only began to go awry when Carrell, the charismatic young offender who became the star of last week's episode, began to lose interest. Gradually, his attendance had slipped to the point that he needed plot recaps at every rehearsal. It began to look increasingly unfair. While Stefan et al struggled with the task at hand, Carrell, sheer charisma making up for his lack of hours, continued to be picked out for extra exposure and given the best positions on stage. Eventually, Gareth saw fit to take him aside. Actually, he did this very well. Asking Carrell what, in the past, he had given 100 per cent to, he elicited the surprisingly moving admission that "there was nothing that springs to mind". He dropped out anyway. "Sometimes you wake up and want Cornflakes," he explained, incomprehensibly. "And sometimes you want Weetabix."

Gosh, can you imagine being Ashley Jensen? One lifetime you're picked out of obscurity to play Ricky Gervais's hopeless sidekick, Maggie, the next you're living in Los Angeles, being offered roles in Hollywood, starring in big hitters like Ugly Betty and patrolling the red carpet. And then you land a leading role in Accidentally on Purpose and... it's awful. The opposite of Extras: unsubtle, overacted, cringeworthy (but not in a knowing kind of way). They even leave long pauses after the jokes before the canned laughter kicks in – presumably to let viewers know that what they just heard was, indeed, a joke even if it wasn't particularly funny. Still, it must have looked good on paper: starring alongside Dharma off of Dharma & Greg (aka Jenna Elfman).

The one redeeming quality – and this, in itself, was probably indicative of the whole thing's utter lack of subtlety – was that despite my not having seen any of the series so far, the plotline was apparent within the first five minutes. Billie, a thirtysomething journalist (played incredibly hammily by Elfman), was pregnant after having a one-night stand with Zack, a twentysomething layabout. She was also incredibly horny, a fact that was somehow converted into the basis for a half-hour script. Should she sleep with anyone? Who should she sleep with? Who does she want to sleep with? Who wants to sleep with her? Riveted? No, me neither.